Well, my experience shows that you are both wrong and the guy at the bike shop was right. Obviously the two ends of the QR are not identical, one has the release lever and the other does not. Clearly they were not seating properly when the QR was the wrong way round. I'm a bit fascinated with the quirk of human nature that makes us all instant experts on any subject we know a little bit about. We hate to have to learn that there's more to something than we already know in spite of the fact that the world is full of evidence that human knowledge on any subject is very limited.